The present invention relates to a timer circuit suitable for operating, for example, the rear windshield defrosting and defogging heater in automobiles, for a required period of time.
In this field, the conventional timer is operated by separate signals produced by a switch in opposite directions, resulting in possible erroneous operation by the car driver. Since transistors of the circuit enter the active region immediately before the timer circuit completes its operation, a supply voltage to relay is caused to fall gradually. Then, a chattering of the relay contacts results.